Note that this is probably not what you are thinking (low-carb, very-low carb or even keto diets are good for your healthspan).
The lowest quintile in this study were consuming 46,4% of kcal from carbs (that's about 230 gram of carbs for a 2000 kcal total intake). Not even close to low carb by today's standard in the health blogosphere.
The authors make this explicit in the discussion section:
>> However, the absence of association between low carbohydrate intake (eg, <50% of energy) and health outcomes does not provide support for very low carbohydrate diets. Importantly, a certain amount of carbohydrate is necessary to meet short-term energy demands during physical activity and so moderate intakes (eg, 50–55% of energy) are likely to be more appropriate than either very high or very low carbohydrate intakes.
One certainly can fuel activity with carbohydrates, but a fat-adapted person should have no trouble with physical activity on a (very) low carbohydrate diet. Interestingly, a fat-adapted athlete can still use carbohydrates for supplemental fuel before, during, or immediately following extreme exertion (no adaptation is required for short-term use of carbohydrates).
The book The Lore of Running covers this as well. For normal day to day things this is fine. However, it is extremely understudied with minimal evidence it works for everyone.
It is still unclear, and dubious to claim, that you can operate at 80+ percent VO2 max on hard work outs. Maybe for short workouts or workouts with bursts of activity e.g. basketball.
You can also undo fat adaptation pretty easily. The answer is it depends, but there is little evidence it has any large negative effects. Questions on peak performance vs "feeling fine" will be interesting to see in studies.
I wonder if many people have tested VO2 max like this. Anecdotally, I know that I have a very difficult time getting my heart rate over 150 if I don't consume carbs, while I can easily get it 160+ if I've consumed carbs. I don't notice a qualitative difference, except during HIIT exercise, but I believe there is a subtle one based on my heart rate.
I have. I found a cool place that did lactate threshold (via constant blood sampling) Dexa fat scans and VO2 max).
The thing is you can use RPE. We basically mean sustained 4/5 effort (rating of perceived on a scale of 1-5). It's a good enough proxy. VO2 max is also tricky because some people have higher or lower VO2 max but go faster or slower. Higher max != Faster times.
I think the sweet spot for very low carb diets is ultra marathon where you keep your HR around 130-140 anyway, wherein you would use fat anyway. Simple fact is you can't max your power output in an aerobic capacity without carbs. This is not disputed. What we want to know is where the cut off point is in terms of percentage of VO2 max.
Edit: just adding, Noakes talks about ultra performance in his book. It covers everything I saw in that book. He dives deep into the body systems and energy production of the body to suss out the science involved.
I have tried it too. I did not PR in the 5k I tried it for. I think on long runs I never noticed, but 50 minute sessions with 5k pace intervals never felt the same zip as I did on carbs. I was consistent with it for 3-4 months so I am sure I was fat adapted. I noticed my water weight was less unstable (my weight didn't fluctuate as much day to day.) I still like periods of low carb, but I found it onnerous to stay I'm that 20g or less range always. Especially with kids and a wife not on the same diet. So I am optimistically on board the low carb diet scheme, it was fine for me. I cautiously think fine for almost everyone. But... :)
Fair to say the study results themselves (as opposed to the authors' assertion quoted in the gp) don't really pertain to the health effect of low carb/keto, at all (ie null rather than evidence for or against)?
Importantly, a certain amount of carbohydrate is necessary to meet short-term energy demands during physical activity [...]
Why would they make such a claim? Anyone who has done keto and worked out has probably had the experience of doing quite a lot of physical activity while having had no carbohydrate intake at all for half a day before, or more.
At most, your brain can run with 75% ketones/25% glucose. Other organs (kidneys, red blood cells, cornea) need about 15-25 grams/carb per day. If you do not get glucose from diet, your body will build it (gluconeogenesis).
Must see if you want to understand/practice keto right:
As far as my research into keto goes eating too much carbs kicks you out of ketosis (duh!) and eating too much protein triggers gluconeogenesis which also kicks you out of ketosis. Which is a shame because I'd be happy to eat fatty steak and fatty pork all the time!
Keto guidelines generally say 30g carbs per day and that's what I'm going to stick to (net carbs; I want to eat avocados!). So typical keto diet should work fine with what you say about carb requirement.
I don't have any particular desire to go all the way to 0 (or some really low number) and if I have some carb budget left I'm happy to get a latte.
Starbucks says grande almond latte has 9g carbs (5g sugars). Perfect to tidy it up to just below 30g/day.
I've been weightlifting for a while and got fitter and stronger but the progress has been slow so I decided to change things up. I read about keto and the more I read the more awesome it seemed.
Since I switched to keto I have an amazing mental clarity. Literally from the moment I open my eyes in the morning I feel lucid (before I'd take me maybe 30 min and maybe a coffee to "wake up"). And I feel lucid all the way until I fall asleep (I don't get tired before falling asleep. Just go to bed, sleep). Nice and steady energy throughout the day.
Also, I feel noticeably better overall. My max strength suffered a little bit (keto can take 1-3 months to adjust) but I'm more energetic throughout the day, mind and body.
Not sure what this other guy will say, but for the vast majority of people it is for major weight loss, not necessarily lifestyle or belief that it is a "superior" health approach. This is my experience from Reddit's keto and loseit communities anyway.
If you do not get glucose from diet, your body will build it (gluconeogenesis).
That is also my knowledge. Therefore, there seems no need for any intake of carbohydrates; So the claim about "needing carbohydrates" is not warranted (about intake, anyway)
I’ve been <20g of carbs per day since February 2016. My athletic performance was impaired for the first 6-8 weeks, but has since increased dramatically.
At low circulating insulin levels, most cells in your body can efficiently metabolize fatty acids. For the minority of cells that cannot, your liver converts protein into sugar by a process known as gluconeogenesis.
It’s very possible to be a performance athlete and eat very low carb.
80m of exercise is enough to deplete muscle glycogen to as-near-zero as makes no difference.
In a sessile starvation state glycogen stops being a meaningful energy source after 2 days, with the majority of it depleted in approximately 8-12 hrs (it's non-linear).
Depending on one's baseline physical activity and what they mean by "half a day," sure, glycogen stores can be reasonably depleted.
That said, glucogenic amino acids can replenish glucose stores, which can ultimately become glycogen. Glycogen remains low only in the context of low-carb and low-total calories, so what glycogen is replenished is soon exhausted.
"Doing keto" implies less than 20g/day on an ongoing basis, at least as I understand it. On top of that, one might have eaten early in the previous day, eaten no breakfast, and be working out about lunch time, which would provide the "at least half a day without carbs of any kind".
It may be that you disagree, but I get the feeling that you ignored the "doing keto" part of my setup, and instead thought that the person in question was eating cake 12.5 hours before the workout. :)
I can achieve 'dark purple' on strips in two to three days without drastic dietary or exercise extremes. This is one of my biggest sticking points with articles that make generalizations about body functions. There are always outlying examples and exceptions.
You probably already know this, but in case other readers don't, the depth of color on keto sticks is NOT a measure of "how deeply in ketosis" you are.
The depth of color indicates how concentrated ketones are in your urine, which is impacted by (1) the amount of ketones your body is producing, and, very importantly, (2) your hydration level (i.e. how diluted your urine is).
For newbies, if the stick is pink AT ALL, congrats, you're in ketosis. Don't make the depth of color a big goal.
A little known fact is that you can induce ketosis while eating carbs. The biochemistry here is clear: You get into ketosis when you oversupply acetyl groups to the TCA cycle. Adding MCT (Medium Chain triglycerides) to your diet will do this.
As someone who has been on a low-carb diet for 3 years, on and off, I definitely don't notice any difference in performance, mood or productivity while on a low-carb diet. Too many people (esp. those in a desk job) over estimate their physical activity levels and think they need more carbs.
Sure, if you're an athlete, all this doesn't apply to you. But, for the vast majority (who in the present day) lead highly sedentary lifestyles, it's about time we encourage them to get off carbs as much as possible.
I think the assumption there is very-low carb (as a macro-nutrient, not "healthy" v "unhealthy") can be better if _lower_ carb demonstrates improved outcomes... ?
That is about what I have been eating naturally (~150-250g carbs daily, pretty much from oats, potatoes, sweet potatoes, dairy, and 1-2 servings of fruit per day).
The key to cheap and non-harmful GNG is to have copious amounts of fats circulating, at a keto-typical low weight that means copious intakes of fats too. GNG ideally shouldn't/wouldn't happen from proteins (unless intake is very high) but from other metabolic byproducts and the glycerol backbones of triglycerides. Then this process typically accompanies ketosis in which ketones (endogenously produced-from-fat-burning types-of-carbohydrate but not from GNG) power most (not all) glucose-but-not-fat-burning-capable cells. Fat-adapted where possible, ketone-adapted elsewhere, and lots of byproducts that ordinarily would be "useless and to be excreted" (not just glycerol but also lactate, pyruvate etc) can now feed into (non-protein) GNG without the complications and expenses and downsides of protein-to-glucose GNG.
Comments
Note that this is probably not what you are thinking (low-carb, very-low carb or even keto diets are good for your healthspan).
The lowest quintile in this study were consuming 46,4% of kcal from carbs (that's about 230 gram of carbs for a 2000 kcal total intake). Not even close to low carb by today's standard in the health blogosphere.
The authors make this explicit in the discussion section:
Anecdatum, but I play competitive basketball on a very low carbohydrate diet (<20g/day), and feel just fine, so necessary seems necessarily false.
The missing concept (in the brief quote in your comment) might be "fat adaptation", which takes (in my experience) 2-4 weeks (details: http://www.artandscienceoflowcarb.com/the-art-and-science-of... )
One certainly can fuel activity with carbohydrates, but a fat-adapted person should have no trouble with physical activity on a (very) low carbohydrate diet. Interestingly, a fat-adapted athlete can still use carbohydrates for supplemental fuel before, during, or immediately following extreme exertion (no adaptation is required for short-term use of carbohydrates).
The book The Lore of Running covers this as well. For normal day to day things this is fine. However, it is extremely understudied with minimal evidence it works for everyone.
https://www.google.com/amp/s/www.runnersworld.com/newswire/d...
It is still unclear, and dubious to claim, that you can operate at 80+ percent VO2 max on hard work outs. Maybe for short workouts or workouts with bursts of activity e.g. basketball.
You can also undo fat adaptation pretty easily. The answer is it depends, but there is little evidence it has any large negative effects. Questions on peak performance vs "feeling fine" will be interesting to see in studies.
I wonder if many people have tested VO2 max like this. Anecdotally, I know that I have a very difficult time getting my heart rate over 150 if I don't consume carbs, while I can easily get it 160+ if I've consumed carbs. I don't notice a qualitative difference, except during HIIT exercise, but I believe there is a subtle one based on my heart rate.
I have. I found a cool place that did lactate threshold (via constant blood sampling) Dexa fat scans and VO2 max).
The thing is you can use RPE. We basically mean sustained 4/5 effort (rating of perceived on a scale of 1-5). It's a good enough proxy. VO2 max is also tricky because some people have higher or lower VO2 max but go faster or slower. Higher max != Faster times.
I think the sweet spot for very low carb diets is ultra marathon where you keep your HR around 130-140 anyway, wherein you would use fat anyway. Simple fact is you can't max your power output in an aerobic capacity without carbs. This is not disputed. What we want to know is where the cut off point is in terms of percentage of VO2 max.
Edit: just adding, Noakes talks about ultra performance in his book. It covers everything I saw in that book. He dives deep into the body systems and energy production of the body to suss out the science involved.
Great comment, I'm curious about all this too. I'd be interested in more precise data than my own vague n = 1 impressions!
I actually spent a fair bit of time delivering VO2 max tests to athletes (in a previous life as an exercise physiology lab volunteer).
This comment has me wondering if I still know any active researchers in this area, looking for ideas...
I have tried it too. I did not PR in the 5k I tried it for. I think on long runs I never noticed, but 50 minute sessions with 5k pace intervals never felt the same zip as I did on carbs. I was consistent with it for 3-4 months so I am sure I was fat adapted. I noticed my water weight was less unstable (my weight didn't fluctuate as much day to day.) I still like periods of low carb, but I found it onnerous to stay I'm that 20g or less range always. Especially with kids and a wife not on the same diet. So I am optimistically on board the low carb diet scheme, it was fine for me. I cautiously think fine for almost everyone. But... :)
OP here. Fully agree. I do 2-3 keto cycles (5 weeks) per year. Not against keto diet.
But note that the context of this study is healthspan and mortality, not athletic performance, weight loss, etc.
It was just warning that this study does not warrant that keto diet is good for your health in the long term. The title is a bit misleading.
Fair to say the study results themselves (as opposed to the authors' assertion quoted in the gp) don't really pertain to the health effect of low carb/keto, at all (ie null rather than evidence for or against)?
Why would they make such a claim? Anyone who has done keto and worked out has probably had the experience of doing quite a lot of physical activity while having had no carbohydrate intake at all for half a day before, or more.
At most, your brain can run with 75% ketones/25% glucose. Other organs (kidneys, red blood cells, cornea) need about 15-25 grams/carb per day. If you do not get glucose from diet, your body will build it (gluconeogenesis).
Must see if you want to understand/practice keto right:
https://www.youtube.com/user/chrismasterjohn/videos
I started a keto diet 2 weeks ago.
As far as my research into keto goes eating too much carbs kicks you out of ketosis (duh!) and eating too much protein triggers gluconeogenesis which also kicks you out of ketosis. Which is a shame because I'd be happy to eat fatty steak and fatty pork all the time!
Keto guidelines generally say 30g carbs per day and that's what I'm going to stick to (net carbs; I want to eat avocados!). So typical keto diet should work fine with what you say about carb requirement.
I don't have any particular desire to go all the way to 0 (or some really low number) and if I have some carb budget left I'm happy to get a latte. Starbucks says grande almond latte has 9g carbs (5g sugars). Perfect to tidy it up to just below 30g/day.
What was your motivation for starting the keto diet?
I've been weightlifting for a while and got fitter and stronger but the progress has been slow so I decided to change things up. I read about keto and the more I read the more awesome it seemed.
Since I switched to keto I have an amazing mental clarity. Literally from the moment I open my eyes in the morning I feel lucid (before I'd take me maybe 30 min and maybe a coffee to "wake up"). And I feel lucid all the way until I fall asleep (I don't get tired before falling asleep. Just go to bed, sleep). Nice and steady energy throughout the day.
Also, I feel noticeably better overall. My max strength suffered a little bit (keto can take 1-3 months to adjust) but I'm more energetic throughout the day, mind and body.
Not sure what this other guy will say, but for the vast majority of people it is for major weight loss, not necessarily lifestyle or belief that it is a "superior" health approach. This is my experience from Reddit's keto and loseit communities anyway.
That is also my knowledge. Therefore, there seems no need for any intake of carbohydrates; So the claim about "needing carbohydrates" is not warranted (about intake, anyway)
Half a day of carb restriction wouldn't meaningfully deplete glycogen stores.
I’ve been <20g of carbs per day since February 2016. My athletic performance was impaired for the first 6-8 weeks, but has since increased dramatically.
At low circulating insulin levels, most cells in your body can efficiently metabolize fatty acids. For the minority of cells that cannot, your liver converts protein into sugar by a process known as gluconeogenesis.
It’s very possible to be a performance athlete and eat very low carb.
80m of exercise is enough to deplete muscle glycogen to as-near-zero as makes no difference.
In a sessile starvation state glycogen stops being a meaningful energy source after 2 days, with the majority of it depleted in approximately 8-12 hrs (it's non-linear).
Depending on one's baseline physical activity and what they mean by "half a day," sure, glycogen stores can be reasonably depleted.
That said, glucogenic amino acids can replenish glucose stores, which can ultimately become glycogen. Glycogen remains low only in the context of low-carb and low-total calories, so what glycogen is replenished is soon exhausted.
...even if you'd already been doing keto on an ongoing basis?
„no carbohydrate intake at all for half a day before“ no way your body was in ketosis.
"Doing keto" implies less than 20g/day on an ongoing basis, at least as I understand it. On top of that, one might have eaten early in the previous day, eaten no breakfast, and be working out about lunch time, which would provide the "at least half a day without carbs of any kind".
It may be that you disagree, but I get the feeling that you ignored the "doing keto" part of my setup, and instead thought that the person in question was eating cake 12.5 hours before the workout. :)
the specific number varies between different people. i'd say <20g is enough to get everybody into ketosis. <50g is enough for some.
It takes about a week of < 20g/carbs a day for the body to go into ketosis. This is born out by buying keto strips and testing your urine.
I can achieve 'dark purple' on strips in two to three days without drastic dietary or exercise extremes. This is one of my biggest sticking points with articles that make generalizations about body functions. There are always outlying examples and exceptions.
You probably already know this, but in case other readers don't, the depth of color on keto sticks is NOT a measure of "how deeply in ketosis" you are.
The depth of color indicates how concentrated ketones are in your urine, which is impacted by (1) the amount of ketones your body is producing, and, very importantly, (2) your hydration level (i.e. how diluted your urine is).
For newbies, if the stick is pink AT ALL, congrats, you're in ketosis. Don't make the depth of color a big goal.
this is not true for all people and urine tests are not considered reliable. I can get into ketosis in a single day of fasting
A little known fact is that you can induce ketosis while eating carbs. The biochemistry here is clear: You get into ketosis when you oversupply acetyl groups to the TCA cycle. Adding MCT (Medium Chain triglycerides) to your diet will do this.
I think this needs a little more explanation. Can you provide that?
Check this out: https://youtu.be/DG79PYeqZ78
It takes 3 days for me to hit ketosis at that carb level.
As someone who has been on a low-carb diet for 3 years, on and off, I definitely don't notice any difference in performance, mood or productivity while on a low-carb diet. Too many people (esp. those in a desk job) over estimate their physical activity levels and think they need more carbs.
Sure, if you're an athlete, all this doesn't apply to you. But, for the vast majority (who in the present day) lead highly sedentary lifestyles, it's about time we encourage them to get off carbs as much as possible.
I think the assumption there is very-low carb (as a macro-nutrient, not "healthy" v "unhealthy") can be better if _lower_ carb demonstrates improved outcomes... ?
That is about what I have been eating naturally (~150-250g carbs daily, pretty much from oats, potatoes, sweet potatoes, dairy, and 1-2 servings of fruit per day).
There’s no such thing as necessary carbohydrates. The body is capable of producing all the glucose it needs.
True, but think about non-necessary vs beneficial vs optimal.
"Gluconeogenesis is extremely expensive" [1]
[1] https://www.youtube.com/watch?v=Og8PTdjVAWE
The key to cheap and non-harmful GNG is to have copious amounts of fats circulating, at a keto-typical low weight that means copious intakes of fats too. GNG ideally shouldn't/wouldn't happen from proteins (unless intake is very high) but from other metabolic byproducts and the glycerol backbones of triglycerides. Then this process typically accompanies ketosis in which ketones (endogenously produced-from-fat-burning types-of-carbohydrate but not from GNG) power most (not all) glucose-but-not-fat-burning-capable cells. Fat-adapted where possible, ketone-adapted elsewhere, and lots of byproducts that ordinarily would be "useless and to be excreted" (not just glycerol but also lactate, pyruvate etc) can now feed into (non-protein) GNG without the complications and expenses and downsides of protein-to-glucose GNG.